Reciprocating pump



Aprii 30, 1968 s. KOFINK 3,380,387

RECIPROCATING PUMP Filed March 14, 1966 2 Sheets-Sheet 1 Fig. 1

hmw me Filed March 14, 1966 2 Sheets-Sheet 2 [I6 106 a 103 b Fig. 2-

United States Patent 3,380,387 RECIPROCATING PUMP Siegfried Kofink, Zell (Neckar), Germany, assignor to J. Eberspaecher, Esslingen (Neckar), Germany Filed Mar. 14, 1966, Ser. No. 534,062 Claims priority, application Germany, Mar. 13, 1965, E 28,877 Claims. (Cl. 103-37) ABSTRACT OF THE DISCLOSURE The invention relates to a reciprocating pump having a cylinder. The cylinder is provided with an inlet opening and, spaced therefrom, with a metering chamber. A piston is received in the cylinder and is reciprocable to perform alternating suction and working strokes. At least one axially extending groove is provided in the circumferential surface of the cylinder and communicates with the inlet opening and, when the piston performs a suction stroke, with the metering chamber. A wall member is received in the cylinder opposite the piston and bounds a portion of the chamber. The wall member is adjustable in the cylinder axially of the piston so as to permit changing of the volume of the chamber.

The present invention relates to reciprocating pumps in general, and more particularly to improvements in metering pumps which may be utilized to discharge accurately metered quantities of liquid fuel or another liquid medium. Still more particularly, the invention relates to improvements in reciprocating pumps of the type disclosed in my copending application Ser. No. 444,097, which is assigned to the same assignee. In such pumps, a piston reciprocates in a cylinder to perform alternating working and suction strokes, and the rate at which the pump discharges fluid is regulated by regulating the frequency at which an electromagnetic drive for the piston is energized or by resorting to a diaphragm type pressure regulator. Both such methods are rather complicated and the provision of frequency regulators or diaphragm type pressure regulators contributes significantly to the initial and maintenance cost of the pump.

It is an important object of the present invention to further improve the construction and operation of pumps which are disclosed in my aforementioned applications, particularly as regards their metering action.

Another object of the invention is to provide a pump of the just outlined characteristics wherein the amounts of fluid which are discharged in response to each working stroke of the piston may be regulated with requisite accuracy without necessitating any changes in the length of such strokes and Without resorting to diaphragm type pressure regulators.

A further object of the invention is to provide a reciprocating pump wherein the piston is reciprocated by electromagnetic means and wherein the rate at which the pump discharges accurately metered quantities of a fluid medium may be regulated while the pump is in actual use and by resorting to very simple, compact and readily manipulable regulating means.

A concomitant object of the invention is to provide a novel check valve which may be used in a reciprocating pump of the above outlined characteristics.

vA further object of the invention is to provide an elec- I trically operated reciprocating pump wherein the check valve which prevents return flow of fluid to the Working chamber of the pump cylinder can perform an additional important function.

Briefly stated, one feature of the present invention resides in the provision'of a recoprocating fluid pump ice which comprises a cylinder defining a metering or working chamber, a piston received in the cylinder and reciprocable to perform alternating working and suction strokes to thereby respectively draw fluid into and to expel fluid from the working chamber, and a wall member received in the cylinder opposite the piston and bounding a portion of the working chamber. In accordance, with by present invention, the wall member is adjustable in the cylinder axially of the piston to thereby change the volume of the working chamber.

In accordance with another feature of the present invention, the wall member may be constituted by the housing of a check valve having a passage through which the fluid is expelled from the working chamber when the piston performs a working stroke. The passage may be controlled by a spring-biased ball or the like to prevent return flow of fluid into the working chamber when the piston performs a suction stroke.

For example, the wall member may be provided with external threads which mesh with internal threads provided in the cylinder so that the effective volume of the working chamber may be changed in response to rotation of the wall member with reference to the cylinder Alternatively, the wall member may be slidable in the axial direction of the piston and may cooperate with a regulating member which is rotatable in the cylinder and is provided with one or more followers tracking a cam face on the wall member so that, in response to angular displacement of the regulating member, the wall member is moved nearer to or further away from the piston. It is clear that the position of the follower and cam face may be reversed, i.e., that the follower may be provided on the wall member. When the wall member is slidable in the cylinder, it is preferably biased by a suitable spring which urges it against the regulating member. The latter is mounted in the cylinder in such a way that it cannot move axially and may be rotated by a suitable lever or the like.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved pump itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings in which:

FIG. 1 is an axial section through a reciprocating pump which embodies one form of the present invention and wherein the wall member is constituted by the housing of a check valve and meshes with the cylinder; and

FIG. 2 is a partly elevational and partly axial sectional view of a modified reciprocating pump wherein the wall member is slidable in the cylinder.

Referring first to FIG. 1, where is shown a reciprocating pump which may be utilized to inject accurately metered quantities of liquid fuel into the cylinders of an internal combustion engine, not shown. The pump comprises a cylinder 7 which is provided with a radially extending outlet 1 adjacent to its upper end and with an axially extending inlet 1b at its lower end. The cylinder 7 is formed with an axially extending bore 7a which receives a reciprocable piston 3. The numeral 2 denotes a check valve which is interposed between the inlet 1b and outlet 1 and whose housing 8 constitutes a wall member serving as a stop for the piston 3 and also as a means for changing the effective volume of a composite metering or working chamber which is constituted by an intermediate portion of the bore 7a. This working chamber comprises an upper portion 6 which can snugly receive the upper-end portion of the piston 3 and a lower portion 6a which can receive the upper end portion-of the piston 3 with at least some radial clearance so that, when the piston performs a suction stroke (by moving downwardly, as viewed in FIG. 1), it can permit fuel to flow from the inlet 1b, into an auxiliary chamber 1a of the cylinder 7, through one or more axially extending grooves 3b which are machined into the periphery of the piston 3, and into the working chamber 6-, 6a. The rod 3a of the piston 3 is coupled to the armature 4 of an electromagnet whose coil 5 surrounds the cylinder 7. When the circuit of the coil 5 is completed, the armature 4 is attracted and moves upwardly to propel the piston 3 into the upper portion 6 of the working chamber and against the lower end face 8a of the housing 8. When the coil 5 is deenergized, the armature 4 is compelled to move downwardly under the bias of a helical return spring 30 which operates in the chamber In between an internal shoulder of the cylinder 7 and an annular shoulder at the upper end of the armature 4. The piston rod 3a preferably consists of diamagnetic material. The arrows a and b respectively indicate the directions in which the fluid enters and leaves the cylinder 7. Instead of being machined into the periphery of the piston 3, the groove or grooves 3b may he provided in the internal surface of the cylinder 7.

When the piston 3 performs a suction stroke and approaches its lower end position (as seen in FIG. 1), fluid flowing through the groove or grooves 311 can enter the lower portion 6a of the working chamber from all sides and fills the upper portion 6 as well as an axially extending outlet passage 8d provided in the housing 8 of the check valve 2. However, when the piston 3 performs a working (upward stroke), fluid can flow back through the groove or grooves 311 only until the upper end face of the piston reaches the annular shoulder 6b between the chamber portions 6a, 6b. From thereon, the piston 3 slides without clearance in the upper portion 6 and expels an accurately metered amount of fluid through the passage 8d, through the lower portion of the internal space 2b in the housing 8, through one or more radial ports 8e of the housing 8, through a circumferential groove 8g of the housing 8, and into the passage defined by the radial outlet 1. Such metered amount of fluid is then admitted into a cylinder of the internal combustion engine which is combined with the improved injection pump. The just described construction of the improved pump is of advantage because there is no need to provide a valve in the inlet lb or elsewhere in the path of fluid which is admitted into the working chamber 6, 6a. The lower end face 8a of the housing 8 serves as a stop and limits the working stroke of the piston 3.

In accordance with my present invention, the housing 8 (which bounds the upper end portion of the working chamber 6, 6a and is located opposite the piston 3) is adjustable with reference to the cylinder 7 by being movable axially of the piston 3. To this end, the housing 8 is provided with external threads which mesh with internal threads 7b provided in the cylinder 7. The upper end portion of the housing 8 is formed with a diametral slot 8m which is accessible upon removal of a threaded cap 17 which is screwed onto the upper end portion of the cylinder 7. The upper portion of the housing 8 is further provided with internal threads to take an adjusting screw 2e which can regulate the bias of a helical valve spring 2d serving to urge a ball 2c against an annular seat provided therefor at the upper end of the passage 8a. The housing 8 may be fixed in a selected axial position by a lock nut which meshes therewith and is interposed between two annular sealing elements 16a, 16b. In order to adjust the axial position of the housing 8, and hence the effective volume of the upper chamber portion 6, the operator must remove the cap 17 and thereby gains access to the slot 2m which can receive the working end of a screwdriver or a similar tool. Such adjustment can be carried out without necessitating even partial dismantling of the pump; in fact, the pump may remain in operation.

t 4 The same holds true for adjustments of the screw 2e.

The cylinder 7 comprises three distinct portions 70, 7d, 7e which are held together by split rings 7f. The numeral 7g denotes a gasket which is interposed between the flange of the portion 70 and the frame 5a of the coil 5.

The sliding fit of the upper end portion of the piston 3 in the upper portion 6 of the working chamber is sufficiently tight to prevent return flow of fluid via groove or grooves 3b, even at the time when the piston 3 is immediately adjacent to the lower end face 8a of the housing 8, i.e., when the piston is about to complete a working stroke. Since the piston 3 can move into actual abutment with the end face 8a of the housing 8, all of the fuel admitted into the chamber portion 6 is expelled in response to completion of each working stroke. Thus, there is no possibility of some fuel remaining in the working chamber.

FIG. 2 illustrates a somewhat modified reciprocating pump wherein the check valve 2 is replaced by a check valve 102. whose housing 108 is slidable axially in a somewhat diiferent cylinder 107. The upper end portion ofthe housing 108 is provided with a cam face 108c which is tracked by one or more followers 10a provided on a rotary regulating cam 11 accommodated in the upper end portion of the cylinder .107 in such a way that its axial position remains unchanged. The shaft 11a of the regulating cam 11 extends upwardly through an annular packing gland 13 which is compressed by a cap 9 meshing with the cylinder 107. A resilient element, here shown as a helical expansion spring 10, operates between an annular shoulder 108k of the housing 108 and an internal shoulder of the cylinder 107 to bias the cam face 108:: against the follower 10a. It is clear that the position of the cam face 108:: and follower 10a may be reversed.

The housing 108 is further provided with an axially extending peripheral guide slot 108k which receives the tip of a screw 14 serving to hold the housing against rotation.

In order to adjust the axial position of the housing 108 (which again constitutes a wall member bounding the upper portion 106 of the working chamber .106, 106a), the operator simply turns the lever 12 to the extent indicated by a suitably graduated scale, not shown. Depending on the direction of angular displacement of the regulating cam 11, the spring 10 will be caused to expand or contract and the housing 108 will change the effective volume of the working chamber.

All remaining component parts of the pump shown in FIG. 2 are identical with the corresponding parts of the pump which was described in connection with FIG. 1 and are denoted by similar reference numerals such as 101, 103, 105, etc.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the followingclaims.

What is claimed as new and desired to be protected by Letters Patent is:

1. In a reciprocating pump, a cylinder having an inlet opening and an axially spaced outlet opening and having an inner circumferential surface extending intermediate said openings and defining a metering chamber communicating with said outlet opening; a piston received in said cylinder and having an outer peripheral surface, one of said surfaces being provided with at least one groove extending axially substantially from said'inlet opening to said chamber for conveying fluid from said inlet opening tosaid chamber, said piston being reciprocable to perform alternating suction and working strokes to thereby in the axial position place said groove into communication with said inlet opening and said chamber to draw fluid into the latter during each suction stroke, and to seal said chamber from said groove and expel fluid from said chamber during each working stroke; and a wall member received in said cylinder opposite said piston and bounding a portion of said chamber, said wall member being adjustable in said cylinder axially of said piston to thereby change the volume of said chamber.

2. A structure as set forth in claim 1, wherein said 'Wall member is constituted by the housing of a check valve having a passage through which the fluid is expelled from said chamber when the piston performs a working stroke.

3. A structure as set forth in claim 1, wherein said wall member is provided with external threads and said cylinder is provided with internal threads meshing with said external threads so that said wall member is adjustable in response to rotation thereof with reference to said cylinder.

4. A structure as set worth in claim 1, wherein said wall member is slidable in said cylinder and further comprising adjusting means for adjusting said wall member with reference to said cylinder.

5. A structure as set forth in claim 4, wherein said adjusting means comprises a regulating member rotatably received in said cylinder and adjacent to said wall member, one of said members having a cam face and the other member having a follower arranged to track said cam face so that, in response to rotation of said regulating member, the Wall member is moved axially of said piston.

6. A structure as set forth in claim 5, further comprising resilient means for biasing said wall member against said regulating member.

7. A structure as set forth in claim 6, wherein said cam face is provided on said wall member and said resilient means comprises a spring inserted between an internal shoulder provided in said cylinder and said wall member.

8. A structure as set forth in claim 1, further comprising electromagnetic means for reciprocating said piston through strokes of identical length; and wherein said chamber has an enlarged portion receiving a portion of said piston with radial clearance when the piston terminates a suction stroke and a second smaller portion concentric with said piston and with said enlarged portion and snugly receiving said piston when the latter performs a working stroke.

'9. A structure as set forth in claim 8, wherein said wall member is provided with a passage communicating with the second portion of said chamber to allow for evacuation of fluid from said second portion when the piston performs a working stroke.

10. A structure as set forth in claim 1, wherein said wall member has a stop face against which the piston abuts upon completion of a working stroke and further comprising means for locking said wall member in selected positions of adjustment.

References Cited UNITED STATES PATENTS 851,262 4/1907 Tatum 2-30-21 X 2,008,809 7/1935 Wyld 230-2 1 X 2,293,684 "8/1942 I-Iolthouse 103-5 3 2,642,719 6/ 1953 Walker 2130-21 X ROBERT M. WALKER, Primary Examiner. 

